Trans-Cyclooctene

trans-Cyclooctene[1]
Names
Preferred IUPAC name
(E)-Cyclooctene
Other names
trans-Cyclooctene
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
EC Number
  • 213-245-5
  • InChI=1S/C8H14/c1-2-4-6-8-7-5-3-1/h1-2H,3-8H2/b2-1+
    Key: URYYVOIYTNXXBN-OWOJBTEDSA-N
  • C1CCC/C=C/CC1
Properties
C8H14
Molar mass 110.200 g·mol−1
Appearance colorless liquid
Density 0.848 g/mL
Melting point −59 °C (−74 °F; 214 K)
Boiling point 143 °C (1 atm); 68-72 °C (100 torr)[2]
Hazards
GHS labelling:
GHS02: FlammableGHS08: Health hazard
Danger
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

trans-Cyclooctene is a cyclic hydrocarbon with the formula [–(CH2)6CH=CH–], where the two C–C single bonds adjacent to the double bond are on opposite sides of the latter's plane. It is a colorless liquid with a disagreeable odor.

Cyclooctene is notable as the smallest cycloalkene that is readily isolated as its trans-isomer. The cis-isomer is much more stable;[3] the ring-strain energies being 16.7 and 7.4 kcal/mol, respectively.[4]

cis-Cyclooctene
in chair conformation		 (Rp)-trans-Cyclooctene
in crown conformation

A planar arrangement of the ring carbons would be too strained, and therefore the stable conformations of the trans form have a bent (non-planar) ring. Computations indicate that the most stable "crown" conformation has the carbon atoms alternately above and below the plane of the ring.[5] A "half-chair" conformation, with about 6 kcal/mol higher energy, has carbons 2,3,5,6, and 8 on the same side of the plane of carbons 1,4, and 7.[5]

All conformations of trans-cyclooctene are chiral (specifically, what some call planar-chiral[6]) and the enantiomers can be separated.[7][8][9] In theory, conversion of between the enantiomers can be done, without breaking any bonds, by twisting the whole –CH=CH– group, rigidly, by 180 degrees. However, that entails passing one of its hydrogens through the crowded ring.[7]

  1. ^ "cis-Cyclooctene". Sigma-Aldrich.
  2. ^ Cite error: The named reference vede1973 was invoked but never defined (see the help page).
  3. ^ Neuenschwander, Ulrich; Hermans, Ive (2011). "The conformations of cyclooctene: Consequences for epoxidation chemistry". Journal of Organic Chemistry. 76 (24): 10236–10240. doi:10.1021/jo202176j. PMID 22077196.
  4. ^ Walker, Ron; Conrad, Rosemary M.; Grubbs, Robert H. (2009). "The Living ROMP of trans-Cyclooctene". Macromolecules. 42 (3): 599–605. Bibcode:2009MaMol..42..599W. doi:10.1021/ma801693q. PMC 2850575. PMID 20379393.
  5. ^ a b Cite error: The named reference selv2013 was invoked but never defined (see the help page).
  6. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "Planar chirality". doi:10.1351/goldbook.P04681
  7. ^ a b Cope, Arthur C.; Ganellin, C. R.; Johnson, H. W.; Van Auken, T. V.; Winkler, Hans J. S. (1963). "Molecular Asymmetry of Olefins. I. Resolution of trans-Cyclooctene1-3". Journal of the American Chemical Society. 85 (20): 3276–3279. doi:10.1021/ja00903a049.
  8. ^ Cope, Arthur C.; Mehta, Anil S. (1964). "Molecular Asymmetry of Olefins. II. The Absolute Configuration of trans-Cyclooctene". Journal of the American Chemical Society. 86 (24): 5626–5630. doi:10.1021/ja01078a044.
  9. ^ Steven D. Paget (2001). "(−)-Dichloro(ethylene)(α-methylbenzylamine)platinum(II)". Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289X.rd119. ISBN 0-471-93623-5.